Well washer



J. JOHNSON WELL WASHER Nov. 15, 1938.

Filed May 27, 1956 Patented. Nov. 15, i938 PATENT OFFICE WELL WASHER Jack Johnson, Taft, Calif., assignor, by mesne assignments, to W. J. Nimmer, Los Angeles,

Calif.

Application May 27, i936, Serial No. 82,032

30 Claims.

6 permit oil or other fluids to flow from the oil sands or other formations carrying the liquid to the interior of the casing and hence when such casings arefso plugged, the flow of oil or other liquid is stopped.

An object and feature of my invention is a washing or cleaning device adapted to develop a high pressure in the oil or other liquid in the casing and hence force this outwardly through the perforations of the casing: and when the pressure is suiiicient the oil or other liquid may be blown back into the formation. A further feature of my invention is in creating the pressure to drive the liquid out of the casing by heating this liquid to a sufficient degree to form vapors or gases which on expansion react against the liquid in the perforated part of the casing and thus blow some of this liquid outwardly.

Another object and feature of my invention relates to a device which may be lowered into the casing of a well and locate a structure having a pressure chamber adjacent a portion of the perforations of the casing, this chamber being defined by upper and lower flexible walls engaging the casing, a portion of the casing and a pipe let down through the casing. 'A liquid transfer chamber is located adjacent the bottom of the pipe so that chamber and through the perforations of the casing. A further object and feature of my invention is the employment of a heating and expansion chamber for the liquid located in the pipe inserted in the casing and above the transfer chamber, there being a valve communication to whereby the liquid heated in the heating chamber causes an expansion of the liquid and. in addition develops vapors or gases which force a. flow of liquid through the valve to the transfer chamber and thence through the perforations in the pipe through. the pressure chamber and out through the perforations of the casing. A detail feature of the construction of the heating chamber and the operation is in employing an electrical heating element and a connector attached to a flexible conducting cable which may be lowered through the pipe and form an electrical con-- nection with the electric heating unit, the return or ground connection being through the pipe. Therefore the pipe with the assembly of the heating unitmay be lowered into a well, the electrical connector on the end of the cable may then be lowered through the pipe and guided in a socket forming an electrical connection to the electric heating unit.

My invention also comprehends the method of 5 washing a well to free the casing of obstructions in the perforations by increasing the internal pressure in thel'iquid in the casing adjacent such perforations confining such liquid to produce a flow under pressure outwardly through the perfol0 rations of the casing. My invention also comprehends maintaining all equalized pressure between the oil in the well at the perforated casing, the pressure chamber, the transfer chamber and the heating chamber except that when for instance, 15 oil in the heating chamber is heated to a suflic'ient extent to form steam from the water and oil emulsion or to develop gas vapors, the blow back through the perforated casing again equalizes the increased pressure in the heating cham- 20 ber.

A further object and feature of my invention is in the removal from the perforated casing of clogging accumulations. The additional heat given to the oil in the heating chamber which is 25 blown into the transfer chamber and hence from the pressure chamber through the perforated casing increases the temperature of the oil adjacent the perforated portion of the casing and thus melts, that is, liquefies the solidified or partly 30 solidified oils. In my invention of course it will be understood that when operating at considerable depths the oil is at a high temperature and high pressure. The heating appliance therefore increases the temperature and forms a gas such 35 as steam or gases from the oil which give a series of explosions at more or less equal intervals. These intervals may be varied by either increasing or decreasing the temperature of the heating unit;

My invention is illustrated in connection with the accompanying drawing, in which:

Figure 1 is a vertical section through the lower portion of an oil well illustrating the bore of the well, a portion of the perforated casing, the oil tubing used in conneciion with an oil pump and my heating q ipment showing the connected heating, transfer and pressure chambers and also the electrical connection to a drop plug and a 50 7 socket, certain parts being shown in elevation.

FigureZis atransverse sectiononalargerscale on the line 2-2 of Figure 1 in the direction of the arrows.

rigureiiisatransversesectionontheaameil' scale as Figure 2 on the line 3--3 of Figure 1 in the direction of the arrows.

In the drawing the lower part of a well bore is indicated by the numeral ii and in this bore is inserted the well casing l2. This has a perforated section with a series of perforations I3. Only a portion of the perforated part of the casing is illustrated. Oil tubing I4 which may be used in pumping the well is used to lower the various operating parts of my equipment, this tubing being of a type which may be connected in various stands or lengths as the oil tubing is lowered in the well. I may use, for instance, oil tubing of a standard size having, for instance, an outside diameter of 3%" and an inside diameter of 2%".

To the bottom of the oil tubing I4 I attach a well washer designated by the assembly numeral 2|). This employs a relatively long oil pipe 2| which is illustrated as having a threaded connection 22 to the lower end of the oil tubing, the pipe being illustrated as having internal threads. A solid plug 23 formed of metal engages shoulders 24 on the inside of the pipe 2| and preferably has the lower end of the oil tubing snugly seating on the upper face of this plug. This tight fit however, is unnecessary if the plug makes an oil tight connection with the tubing. As the tubing is lowered stand by stand, it should be maintained empty. A valve plug 25 is fitted in the pipe 2| and is illustrated as being held in place by screws 25 or any other suitable means. There is thus a heating chamber 21 formed within the pipe 2| between the upper plug 23 and the valve plug 25. In this heating chamber there is a supporting diaphragm or spider 28 in which is mounted an electrical heating unit 29. This unit is a relatively long structure and of less diameter than the inside of the pipe 2| so that it may be completely surrounded by oil. The diaphragm or spider 28 is shown as having an upper ring 30 engaging a rim 3| on the upper end of the electric heating unit. This unit may be in the form of a pipe closed at its lower end with electric heating elements therein. There are a series of perforations 32 through the diaphragm 28 to permit flow of oil. The oil has an inlet to the heating chamber through an aperture 33 in the side of the pipe 2| above the heating element and to this is connected an elbow pipe 34 with a ball check valve 35 engaging the seat 36 of the elbow 34, the ball being confined by a cage 31.

At the bottom of the pipe 2| is located a blowoif valve plug 43. This has a-cylindrical section 4| externally screw threaded and threaded on inside threads on the lower end of the pipe 2|. A horizontal partition 42 has a perforation 43 therein forming a port for a valve. A ball valve 44 seats on the underside of the horizontal partition 42. A spring 45 presses the ball upwardly and the tension of this spring may be adjusted by its lower spring ,seat 46 being mounted on a screw 41 threaded through the head 48 of the plug 43. This head has a series of perforations 43 to blow out the 011 should the pressure become excessive. The valve plug 25 has a port 50 closed by a ball valve 5|, this being upwardly pressed by a spring 52 seated in a cage 53, thus a. transfer chamber designated 54 is formed in the pipe 2| between the upper valve plug 25 and the blow-off valve plug 40. The pipe 2| in this section has a series of perforations 55.

Connected adjacent the upper and lower por tions of the transfer chamber and on the outside of the pipe 2| are packing cups 60. These cups are illustrated as having cup-shaped and flexible wall members 6| which may be formed of heavy rubber having an inside central opening 62 of sufllcient size to fit on the outside of the pipe 2|. The cups terminate at an annular rim 63. The packing cups are confined by an outside collar 54 and an inside collar 65, both of these collars being illustrated as attached by screws 66 to the.

oil pipe 2|. These collars are shaped where they contact the resilient packing cups to the shape of the cups and hence firmly confine and attach the cups to the outside of the pipe 2|. In this construction the lower cup has its flexible wall 8| extending upwardly with the rim 63 uppermost whereas the upper cup has the rim 53 lowermost and the wall converging upwardly to the circle of attachment to the outside of the pipe 2|. There is thus formed a pressure chamber designated 61 defined at the top and bottom by the two cups 60, the portion of the casing between these cups and the portion of the pipe 2| also between the cups, that is, this pressure chamber is the section of the casing cut off so far as pressure is concerned from the other part of the casing and outside of the transfer chamber 54. a

The electrical connections are as follows: An insulating socket 10 has a lower portion 1| which extends through an opening in the solid upper plug 23. This socket has an upper flared portion 12. An electrical conductor 13 extends through the lower portion 1| of the socket and an insulating conductor 14 extends from this conductor to a terminal 15 on the heating unit 29. A second terminal 16 is connected by an insulated lead 11 to a terminal screw connection 18 to the oil pipe 2| thus forming the return electrical connection. The upper end of the conductor 13 has a contact end 19 in the socket 10, this socket having perforations to release oil therefrom.

An electric plug element is illustrated as having an insulating body 85 with a metal sheath such as lead, 81, to give weight around. the upper portion thereof, the lower portion 88 being tapered. An electrical conductor 88 extends through the insulating portion of the plug and has a contact end 90 to engage the contact end 19 of the conductor 13 in the socket. A flexible insulated electrical conductor 9| is secured to the upper end of the plug 85 and electrically connected to the conductor 89. This cable may be used to lower the weighted plug 85 through the oil tubing when the washing device is located at the desired place in the well, the tapered end of the plug being guided by the socket to a proper seat and any oil in the plug being expelled through the perforations 80 in order to secure a good electrical contact between the plug 7 and the socket.

The manner of operation and functioning of my invention is as followsi It will be understood that as the oil tubing is filled withoil that the pressure is equalized inside and outside of this tubing in the casing. Also oil flows from the casing inwardly through the port 33 and the valve 35, thus filling the heating chamber 21 with oil. -Also oil enters the transfer chamber either through the valve port 50 or the perforations 55 in the oil pipe. The oil in the heating chamber 21, the transfer chamber 54 and the pressure chamber 61 will thus be at the same pressure and the resilient packing cups 60 forming the top and bottom of the pressure chamber. The electric circuit is closed at the top of the well, thus causing the electric current to flow through the flexible conductor 9|, the conductor 89 in the plug through the socket, the lead 14 to the heating unit 29 and having a return through the return lead TI to the ground connection at 18 to the pipe 2| and hence to the oil tubing, thus giving a complete return circuit. As the heating unit becomes hot, that is, its temperature increases above that of the surrounding oil, any

water contained in this oil and adjacent the heater generates steam and also any gases in the oil which gasify at the increased temperature and. at the pressure of the well develop into a gas or a gaseous vapor.

The device then acts in washing by a series of explosions, that is, when the pressure in the heating chamber accumulates to a sufficient extent to overcome the action of the ball valve 5| which is normally maintained on its seat by quite a strong spring 52, there is a blow passed of the oil in the heating chamber through. the port 5|] to the transfer chamber 54. The ball valve 44 is maintained against its seat by a much stronger spring 45, hence the, pressure developed in the transfer chamber 54 is relieved by the oil blowing out through the perforations 55 in the tube 2| and thence through the pressure chamber 61 and through the perforations l3 in the casing. This gives a back fiow of oil through the casing at this section of the well.

An additional action is given by the increased temperature of the oil in the heating chamber 21 which, when this blows downwardly through the port 50 to the transfer chamber, it increases the temperature of the oil in this chamber and hence oil of a hotter temperature than that of the well is blown out through the perforations in the casing and hence functions to liquefy by increased .temperature constituents of the oil which may have solidified adjacent the inside or out side of the casing. Hence, the perforations are cleaned or washed by a positive outflow of oil under increased pressure and also by the increase of temperature of this oil.

It will be understood that when the device is properly positioned for cleaning a section of the perforated casing and the well formation adjacent thereto and either oil or the solvent solution fills the space between the oil pipe 2| and the well casing above the inlet 33, that the pressure in the heating chamber -21 and annular body of liquid outside of this chamber are at the same pressure.- Also the pressure in the transfer chamber 54 and the pressure chamber 61 are at the same hydraulic pressure, also that the only difference between the pressure at thecheck valve the oil or liquid and of the formation depending on the depth of the well, the temperature as a rule increasing by regular increments as the device is lowered to greater depths in the well.

When the hydraulic heating unit 29 is energized it heats the liquid confined in the heating chamber 21 and if this is the solvent solution it contains a large proportion of water and if oil it also probably contains water or gases which volatize. The increase of pressure due to the formation of gas, this being either steam or the natural gases from the oil, close and hold the inlet valve 35 closed. Also the spring 52 is designed to hold the ball valve 5| seated against a predetermined pressure. This spring is so designed that a considerable difference of pressure in the heating chamber over the transfer chamber is necessary before the valve 5| is forced open. Therefore before this opens a considerable volume of gas including steam is developed in the heating chamber. It expands with an explosivelike action and when the check valve 5| is once opened there is a quick rush of liquid from the heating chamber 21 to the transfer chamber 54, some of which is probably at a high enough temperature so that it develops a gas in the transfer chamber 54. The inflow of fluid into the transfer chamber 54 manifestly forces the surplus out of this chamber .through the pressure chamber 6'! and through the perforations in the casing into direct contact with the wall of the oil well. As soon as the pressure has been released in the heating chamber 21 the valve 5| closes and if the valve 35 could not open, would leave a reduced pressure below that in the liquid surrounding the oil pipe 2| adjacent the inlet aperture 33. Moreover a certain amount of the steam or gases developed will condense. The outside pressure in forcing even a small amount of relatively cool -uid from theoutside of the oil pipe 2| and this may be either oil or a solvent solution, to flow into the heating chamber 21 to fully fill such chamber. The operation is then repeated. If for any reason the pressure of the liquid in the transfer chamber 54 becomes too great and cannot be relieved by an outflow through the perforations l3, the relief blow-off valve opens and the strength of the spring may be so regulated that there can never be a pressure in the transfer chamber 54- sufficient to prevent the explosive flow of liquid from the heating chamberZl tothe transfer chamber 54.

As the increase of pressure in the heating chamber 21 causes a firm closing of the ball valve 35, none of the oil of this chamber can blow out through the port 33. However, when the pres sure developed in the heating chamber 21 is released through the unseating of the ball valve 5| and there is a positive outflow of oil from this heating chamber, oil flows in to the port 33 and past the ball valve 35 to replenish the oil in the heating chamber 21. This again becomes heated until steam or gas, or gas vapors are developed. These again, when the pressure is sufiicient, cause a second explosive action. This cycle may be repeated until it is concluded that the section of the casing confined between the packing cups 60 is thoroughly cleaned and washed. The oil tubing with the assembly is then raised slightly andthe operation repeated. The frequency of the explosive actions is readily detected at the top of the well and hence the operator can either by increasing the temperature of the heating unit 29 or reducing this temperature by varying the current, change the frequency or periods of these explosive actions. I when the operation of washing theperforated section of the casing is complete, the device as a whole is removed from the well by first pulling up the plug 85 by its insulated cable 9i and then hoisting by the oil tubing.

In the method or manner of operating my invention forwashing an oil well, prior to inserting the washer in the well, that is, in the casing, I dump about 3 /2 barrels of what is termed a chemical solution into the well, this solution is usually a strong caustic soda solution, however, other chemicals may be used such as sulphuric acid, when it is desiredto cutmud and fine sand. In the ordinary hole having the usual size of casing, this quantity of 3 /2 barrels of chemical solution makes a column about 100 feet in height.

This is heavier than the oil in the well and hence will settle at the bottom and the oil be supernatant on the caustic solution. This supernatant oil is bailed out otherwise there would be too much pressure at the bottom of the hole and in slushing the hot solution through the action of the electric heater, would drive the bottom settlings lining the walls of the hole into the formation, which should be avoided. If the natural action of the oil should cause the oil to rise during the operation of the washer and form a column above the caustic solution. no harm would be done, as the pressures will be equalized and the effective washing of the well will not be interfered with. My procedure of a washing wells, while mainly designed for use on oil wells which are clogged up, it will be understood that it may be used on new wells before being brought in and before the pumping starts. The action of the electric heater on the caustic solution causes the formation of steam, at least until this solution hasbeen displaced by the oil. The heated liquid assisted by the chemicals will clean out the perforations and softenand emulsify the bottom settlings. The washer is then removed from the well and the liquid at the bottom consisting of the caustic solution, oil and sand, also the supernatant oil, may be bailed out.

Various changes may be made in the details of the. construction without departing from the spirit or scope of the invention as defined by the appended claims.

I claim: p

1. In a method of well washing in which a casing having perforations is installed in the well comprising providing a liquid transfer chamber in the casing communicating with a portion of the casing adjacent the perforations, confining the liquid in the casing from upward or downward flow adjacent the said'perforations, creating a sudden localized pressure in the transfer chamber and forcing the liquid outwardly by such pressure through the confined space and the perforations of the easing into the well formation.

2. In a method of well washing as claimed in claim 1, replacing the liquid discharged from the transfer chamber from a portion of the casing above theliquid confined adjacent the perforations.

3. In a method of well washing as claimed in claim Lincreasing the pressure in the transfer chamber by suddenly forcing heated liquid into such chamber. 4

4. In a method of well washing in which a casing having perforations is located in a well and in which a tubular structure is inserted, said structure having a transfer chamber and a confining means to confine liquid in the casing above and below a series of the perforations, there being transfer openings through the, said structure to a pressure chamber inside of the casing between the confining means comprising forcing a locally heated liquid under a high pressure into the transfer chamber and from the transfer chamber through the pressure chamber and the perforations of the casing.

5. In a method of well washing as 'claimed in claim 4, heating a body of liquid confined to prevent ready fiow of such liquid, developing a gas in the heating of the liquid, such gas being operative to force a portion of the heated liquid into the transfer chamber and to thereby force liquid from the transfer chamber through the pressure chamber and the perforations.

6. A well washer for a perforated well casing comprising in combination apipe insertable in the well, saidpipe having a transfer chamber with lateral outlets and having a confining means to restrict the upward and downward flow of liquid between the'casing and the said pipe, means to suddenly increase the pressure on the liquid in the pipe in the transfer chamber and to force the liquid from said chamber outwardly into the space between the pipe and the casing and thus clean the perforations in the casing, means to create the pressure in the transfer chamber comprising a heating chamber for enclosing a liquid to be heated, a valve connection between the heatingand the transfer chamber whereby the development of gas in the heating chamber from heating the liquid therein causes a sudden flow of liquid through the valve from the heating chamber to the transfer chamber.

7. A well washer for a perforated well casing comprising in combination a pipe insertable in the casing, said pipe having plugs spaced apart at its lower end forming a transfer chamber between the plugs, there being openings in the pipe from the transfer chamber, a flexible packing means attached to the pipe above and below the transfer chamber and forming with the casing an annular pressure chamber surrounding the pipe, the upper plug of the transfer chamber having a port therethrough whereby liquid in the pipe above the upper plug may flow downwardly through the port to the transfer chamber and means to create a sudden pressure on the liquid in the pipe above the upper plug and thereby force a downward flow of liquid into the transfer chamber and from the transfer chamber through the openings in the pipe to the pressure chamber and thence wash the perforations in the casing.

8. A well washer as claimed in claim 7, the means for creating the pressure in the liquid above the upper plug comprising an upper closure for the pipe forming between said closure and the upper plug a heating chamber with a heating ele- 9. A well washer for a perforated well casing comprising in combination a pipe insertable in the casing, said pipe having a closure at the bottom, a valve plug spaced thereabove defining a transfer chamber below the valve plug, there being lateral openings in the pipe from the transfer chamber, a packing means connected to the pipeabove and below the said openings to engage the casing and prevent upward or downward flow of liquid between the casing and the pipe, an upper closure member for the pipe defining a heating chamber between said closure member and the valve plug with an electric heating elemerit therein, a valved connection between the heating chamber and the space between the pipe and the casing, an electrical connection through the upper closure member to the electric heating element whereby the said element develops a gas in liquid in the heating chamber, the expansion of the gas expelling liquid from the heating chamber through the valved plug to the transfer chamher and from the transfer chamber through the openings therein and the space between the upper and lower packings and outwardly through the perforations of the casing.

, 10. A well washer as claimed in claim 9, the bottom closure for the pipe having a blow-off valve to relieve excess pressure in the transfer chamber.

11. A well washer as claimed in claim 9, tubing connected to the said pipe for lowering the said pipe in the casing, an electrical connection through the upper closure to the heating element and electric conducting cable extending downwardly through. the tubing and electrically con nected to the connection through the upper closure member to the heating element.

12. A well washer as claimed'in claim-9, the electrical connection through the upper closure member to the heating element comprising the upper closure member being in the form of a plug with an insulated socket therein with an electrical connector'through the plug, tubing connected to the upper end of the pipe for lowering the pipe into the well and withdrawing the pipe, an electric conducting cable having a plug at its lower end, the plug engaging in the said socket and forming an electrical connection to the heating element.

v 13. A well washer comprising in combinationdrill tubing, a pipe connected to the bottom ofthe tubing, an upper plug separating the pipe from the tubing and having an insulated socket therein with an electrical conductor through the plug, a conducting cable with an insulating plug with a conductor therethrough inserted through the tubing, the plug having an electrical conductor forming a contact with the conductor of the socket, a valve plug intermediate the length of the pipe and abottom plug with a blow-ofi valve thereby forming a heating chamber be tween the plug having the socket and the valved plug, an electric heating element therein, an electrical connection from the socket to the heating element and a return connection from the heating element to the pipe, an inlet valve to the heating chamber communicating with the exterior-of the pipe, the portion of the pipe between the valved plug and the blow-off valve forming a transfer chamber and having openings therethrough, cupped packings of resilient material attached to the outside of the pipe below and above I the said openings whereby on development of a the said cupped packings being adapted to engage the inside of a perforated casing and form part of a pressure chamber whereby pressure may be developed in liquid between the portion of the pipe having the openings anda perforated portion of the casing, the inlet valve in the heating chamber being adapted for inflow of liquid from a space between the pipe and the casing to replenish the liquid forced from the heating to the transfer chamber.

14. In a method of well washing to clean a perforated casing having oil in the lower portion thereof, comprising dumping a cleansing solution into the casing, said solution including water inits composition, the cleansing solution being adapted to displace the oil whereby the cleansing solution occupies a portion of the casing having perforations, confining a portion of the cleansing solution above and below some of the perforations of the casing to prevent upward or downward flow of the confined solution developing steam in another portion of the solution, creating a sudden pressure on the solution so confined by the ,steam and forcing some of the said confined-solution outwardly through the perforations of the casing.

15. In the method of well washing as claimed in claim 14, developing the sudden pressure in the confined cleansing solution by heating another portion of the cleansing solution to develop steam and by the expansion of thesteam forcing a cleansing solution into the confined solution and thereby displacing some of the confined solution outwardly through the perforations of the casing and replacing the portion of the heated cleansing solution by relatively cool fresh solution.

16. In the method of well washing, to clean a perforated casing having oil in the lower portion thereof comprising dumping a cleansing solution into the casing, said solution including water in its composition, the cleansing solution displacing the oil whereby the cleansing solution occupies a portion of the casing having perforations, inserting in the well a tube having a lower perforated transfer chamber and a confining means outside of said'chamber preventing upward and downward fiow of liquid at the sections of the casing to be cleansed and thereby forming a pressure chamber between the confining means, the tube having a solution heating chamber above the transfer chamber, filling the transfer chambers, the pressure chamber and the heating chamber with the cleansing solution, heating the solution in the heating chamber, developing an explosive-like flow of cleaning solution from the heating chamber to the transfer chamber and thence outwardly through the pressure chamber and the perforations of the casing.

17. In the method of well washing as claimed in claim 16, after the explosive flow of solution from the heating chamber replenishing the solution in the heating chamber from the solution in the casing surrounding the pipe.

18. In a method of well washing in which a casing having perforations is installed in the well comprising providing a liquid transfer chamber in the casing communicating with a portion of the casing adjacent the perforations, confining the liquid in the casing from upward or downward flow adjacent the perforations, forcing liquid into the transfer chamber by an explosive-like action by heating the liquid forced into such chamber to develop a gas therein, the

liquid forced into the transfer chamber driving the confined liquid in the casing outwardly through the perforations of the easing into the well formation.

19. In a method of well washing in which a casing having perforations located in a well and in which a tubular structure is inserted in the well, such structure having an upper heating chamber, a transfer chamber therebelow and a confining means between ,the tubular structure and the casing to prevent upward and downward flow of the liquid in the well adjacent the series of perforations of the casing to be cleaned, the confining means developing a pressure chamber inside the casing, the said chambers'being filled with liquid, comprising heating the liquid in the heating chamber to develop a gas in such chamber causing the expansion of the gas to force some of the liquid from the heating to the transfer chamber, the liquid forced into the transfer chamber ejecting liquid from such chamber into the pressure chamber and ejecting the liquid from the pressure chamber through the perforations of the casing.

20. In a method of well washing as claimed in claim 19, replacing the liquid discharged from the heating chamber by relatively cool liquid from within the casing outside of the said tubular structure above the pressure chamber.

21. In the method of well washing to clean a perforated well casing in which a liquid inthe casing is confined on the inside thereof from downward and upward fiow adjacent perforations in the casing comprising forcing a substantially predetermined amount of locally heated liquid mixed with the confined liquid outwardly through the perforations of the casing. p

22. In a method of well washing in which a casing having perforations is installed in a well and a tubular structure having a transfer chamber with perforations is positioned in a'well and the tubular structure has confining means between said structure and the casing to prevent upward or downward fiow of liquid and thereby define a pressure chamber between the i,

perforated transfer chamber and the perforated casing, the transfer chamber and the pressure chamber being filled with liquid, flowing a substantially predetermined amount of locally heated liquid into the transfer chamber and forcing a mixture of the heated liquid and the liquid in the transfer and pressure chambers outwardly through the perforations of the casing.

s 23. A well washer for a perforated well casing comprising in combination a tubular structure inserted in the casing and having a confining means between said structure and the easing to prevent upward and downward fiow of liquid adjacent the perforations of the casing and thereby forming a pressure chamber between cheat and to fiow a substantially predetermined quantity of similar liquid into the transfer chamber and thus develop a flow of the mixture of the heated liquid and the liquid in the transfer and pressure chamber outwardly through the perforations of the casing.

24.-A well washer as claimed in claim 23, the

tubular structure having a heating chamber positioned above the transfer chamber with a heating element therein to heat the liquid in the heating chamber, such heated liquid bein adapted to flow into the transfer chamber.

25. A well washer for a perforated well casin comprising in combination an elongated pipe insertable in the well and having an upper heating chamber, a lower transfer chamber, the pipe at the transfer chamber having perforations, confining means secured to the pipe above and below the perforations at the transfer chamber and engaging the casing and forming a pressure chamber between the perforated section of the pipe, the casing approximate thereto and the confining -means, said chambers being adapted to contain liquid in the well and well casing,

means to locally heat the liquid in the heating chamber, means to confine the heated liquid from upward fiow whereby the heated liquid fiows into the transfer chamber, thereby a mixture of the heated liquid and the liquid in the transfer chamber flows out through the perforations of the pipe through the pressure chamber and through the perforations of the casing.

26. A well washer as claimed in claim 25, the means confining the heated liquid comprising a check valve adapted for inward flow of liquid from a space between the casing and the pipe above the confining means and there being a pressure release valve between the heating and the transfer chambers.

27. A well washer for a perforated well casing comprising in combination a structure insertable in the casing and having a first confining means for a first body of liquid, a second confining means to confine a second body of liquid in the casing for upward or downward flow adjacent a series of perforations of the casing, means to suddenly develop a gas in the first confining means to thereby increase the pressure in the first confined liquid, means to fiow some of the first confined liquid into the second body of confined liquid and thereby increase the internal pressure in the second confining means and force a portion of the second confined liquid outwardly through the perforations of the casing.

28. In a method of well washing to clean a perforated casing comprising confining the liquid in the well on the inside of the casing from downward and upward flow adjacent perforations in the casing, then suddenly creating a localized pressure and reacting such pressure on the confined liquid and forcing such liquid outwardly through perforations and into the formation outside of the casing.

29. In a method of well washing as claimed in claim 28, in the creation of the local pressure and its reaction on the confined liquid increasing the temperature of the liquid forced outwardly through the perforations.

30. In the method of well washing to clean a perforated casing comprising confining a first liquid inside a perforated portion of the casing from upward and downward flow adjacent such perforations, confining a second body of liquid, producing an explosive-like development of the gas in the second body of liquid to thereby increase its pressure, flowing a portion of the second body of liquid into the first confined liquid to increase the internal pressure of the first liquid and thereby forcing some of the first liquid outwardly through the perforations.

JACK JOHNSON. 

